Yep, as far as I know the "10% + X" rule is pure conjecture. If its illegal for speedos to under read, why would they then have a rule that takes into account under reading speedos? Perhaps there is an unwritten rule that the authorities use, but i'm fairly sure there is no Law as such. If you get caught doing over the speed limit, you open yourself up to a moody/bored copper.

Forgot to mention I'm a biker too - there are bikers that ride like idiots but it's a pretty small minority, albeit that they are the ones you remember.

As for cutting in and out, if I'm on a motorway and someone won't pull over I'll ride in whichever lane is most appropriate....as the middle and outside lanes are actually designated as overtaking lanes that means riding in the inside / middle at a greater speed than the outside lane is going at times. Remember that a bike can get out of your way a lot faster than a car, and as DX mentioned we know we're more vulnerable when on a bike so are generally less likely to ride outside our skill envelope, though I do appreciate this is not always the case. I'm waiting for someone to complain about filtering next though

I just hate it when sat in traffic when a bike..... Hahaha I couldn't resist satori!